My little diva has refused the boob during the day since she was about 2 months. She only drinks "live" during her early morning dream-feed at about 5/6 a.m.
She would start screaming and crying and to be honest made me feel really bad about it. Since I was returning to work at 12 weeks I decided to just go with it and start expressing almost exclusively. I have the Medela Swing pump and so far it's doing the job pretty well.
I get up at 6.30, do both breasts which gets me about 300ml. At work I pump at 10.30, 12.30 and 15.30 and I get 150ml. from each session. When I get home I pump once or twice. At the moment I have too much milk (150ml goes into the freezer every day), but since I'm planning to BF 6 months exclusively I want to keep that production high.
On the days that I don't work I'm more relaxed about it, only pump "on demand" so to speak.
I do get comments from people (also women that have BF themselves) that I will get fed up, or should just switch to formula, but that thought has never crossed my mind. I really don't mind doing it, my little girl is doing great, she's happy and healthy.
I plan to go on until she's 1 and lately have been contemplating about continueing after that. She will eat other food as well, so I will need a lot less milk anyway.
Moral of my story is to just do what makes you and your baby happy. There aren't any rules when it comes to babies. Listen to advice, but do what suits your situation!